In a production line of a semiconductor substrate, a thin-film substrate, etc., inspection of defects on a surface of the semiconductor substrate, the thin-film substrate, etc. is performed in order to keep and improve the yield rate of products. As the background art, there is a method of “irradiating a wafer surface with a laser beam condensed into a size of tens of micrometers, condensing and detecting scattered light generated from each defect, and detecting each defect having a size of from the order of tens of nanometers to the order of micrometers or more”. Patent Literature 1 (JP-A-9-304289) and Patent Literature 2 (JP-A-2000-162141) have been known as the background art.
In Patent Literature 3 (JP-A-2008-268140), there has been disclosed a method of “illuminating one and the same defect several times in one inspection with an illuminating optical system for performing linear illumination and a detecting optical system for performing detection while splitting an illumination-target region by a line sensor, and adding the scattered light to thereby improve the detection sensitivity”.
As a method for reducing a detection error caused by change in height of a wafer during inspection, in Patent Literature 4 (JP-A-2007-240512), there has been disclosed a method of “illuminating a surface of a rotating water with a beam emitted from a first light source to form a beam spot, detecting scattered light caused by a defect such as a foreign matter on the wafer surface in a plurality of detections to output signals, detecting vertical motion of the wafer surface by using white light or broadband light from a second light source, correcting the position of the beam spot on the wafer surface based on information of the vertical motion of the wafer surface to suppress coordinate error caused by the vertical motion of the wafer surface, correcting the direction and position of emission of light from the first light source to suppress coordinate error caused by change in the first light source to thereby improve coordinate accuracy of the defect such as a foreign matter to be detected, further correcting the diameter of the illuminating beam spot to suppress an individual difference in detection sensitivity or foreign matter coordinate detection error between devices”.